1.) Rn-222 decays from 400 grams to 6.25 grams in 240 minutes. How long is one “half-life.

A ball is thrown vertically upward from the edge of a bridge 22.0 m high with an initial speed of 16.0 m/s. The ball falls all t

KonstantinChe [14]

To solve this problem we will apply the concepts related to the kinematic equations of motion. We will start calculating the maximum height with the given speed, and once the total height of fall is obtained, we will proceed to calculate with the same formula and the new height, the speed of fall.

The expression to find the change in velocity and the height is,

$v_f^2-v_0^2 = -2gh$

Replacing,

$0^2-16^2 = -2(9.8)h$

$h = 13.0612m$

Thus the total height reached by the ball is

H = 22m+13.0612m

H = 35.0612m

Now calculate the velocity while dropping down from the maximum height as follows

$v_f^2-v_0^2 = 2gh$

Substituting the new height,

$v_f^2 - 0^2 = 2(9.8)(35.0612)$

$v = \sqrt{687.2}$

$v = 26.2145m/s$

3 0

3 years ago

Which of the following is the best hypothesis

tekilochka [14]

Answer:

Melting and frezzing are physical changes

5 0

3 years ago

sketch a graph of position vs. time for a person starting 0.4 m away and standing still. Include an explanation of your predicti

Korvikt [17]

Answer:

Straight line parallel to time axis.

Explanation:

The slope of the position time graph gives the velocity.

As the man is still, that means the velocity is zero. So, the slope of the graph is zero. It is a straight line parallel to time axis.

5 0

3 years ago

When doing scientific research ,the sources used should be ?

quester [9]

Answer: Reliable and trusted

6 0

3 years ago

Read 2 more answers

You, Archimedes, suspect that the king’s crown is not solid gold but is instead gold-plated lead. To test your theory, you weigh

hjlf

Answer:

a) 16675.75 Kg/m³ b) 77.6%

Explanation:

the weight of the crown = 60 N, density of gold = 19300 Kg/m^3, density of lead = 11340 kg/m^3, density of water = 1000kg/m^3 and acceleration due to gravity = 9.8 m/s^2

upthrust on the crown = weight in air - weight when fully submerged in water = 60 - 56.4 = 3.6 N

mass of water displaced = 3.6 / 9.8 since weight = mass × g

mass of water displaced = 0.367 Kg

density of water = mass / volume

1000 = 0.367 / volume

cross multiply and find volume

volume of the crown = 0.367 / 1000 = 0.000367 m³ since the crown will displace water of equal volume according to Archimedes principle

Let V1 represent the volume of Gold and let V2 represent the volume of lead

Total volume of the crown = V1 + V2

also

density of gold = mass of gold / V1 and density of lead = mass of lead / V2

19300 = mass of gold in the crown / V1 and 11340 = mass of lead in the crown / V2

19300 V1 = mass of gold and 11340 V2 = mass of lead

add the two together

19300 V1 + 11340 V2 = weigth of the crown / 9.8

19300 V1 + 11340 V2 = 6.12 also

V1 + V2 = 0.000367

make V1 subject of the formula in equation 2

V1 = 0.000367 - V2

substitute for V1 in equation 1

19300 (0.000367 - V2) + 11340 V2 = 6.12

open the bracket

7.083 - 19300 V2 + 11340 V2 = 6.12

rearrange the equation

-7960 V2 = 6.12 - 7.083

-7960 V2 = -0.963

V2 = -0.963 / -7960 = 0.000121 (volume of lead in the crown)

substitute V2 into equation 2

V1 + 0.000121 = 0.000367m³

V1 = 0.000367 - 0.000121 = 0.000246m³ (volume of gold in the crown)

so mass of gold in the crown = 19300 × 0.000246 = 4.748 kg

and mass of lead = 11340 × 0.000121 = 1.372 kg

average density of the crown = (mass of gold + mass of lead) / total volume = 6.12 / 0.000367 = 16675.75 kg/ m³

b) percentage make of gold = mass of gold / total mass × 100 = 77.6 % approx

4 0

3 years ago